Simulic
English

Breathing mechanics, spirometry and gas exchange

BiologyHuman & Animal PhysiologyAges 16–17

Loading…

Use with my class ✨ Customize with AI Report a problem

The diaphragm and intercostal muscles change the volume of the thorax, so the pressure in the lungs falls or rises (Boyle's law) and air moves in or out; compare the chest with the bell-jar model. A spirometer traces lung volumes: tidal volume, vital capacity, FEV₁/FVC and pulmonary ventilation = tidal volume × breathing rate. Switch between healthy lungs, asthma, emphysema and fibrosis, add smoking or exercise to see the effect on gas exchange in the alveoli, and run the limewater practical with inhaled and exhaled air.

Lesson: Gas exchange and ventilation in humans

What it shows

Breathing in happens when the diaphragm and external intercostal muscles contract: the thorax gets bigger, the pressure in the alveoli falls below atmospheric pressure (Boyle's law) and air flows in. Quiet breathing out is passive recoil; forced breathing out uses the internal intercostals and abdominal muscles. A spirometer measures tidal volume, inspiratory and expiratory reserve volumes, vital capacity, FEV₁ and FVC. Obstructive diseases such as asthma and emphysema lower FEV₁/FVC; fibrosis makes the lungs stiff and small. In the alveoli, Fick's law links the rate of diffusion to surface area, concentration difference and thickness.

How to use

In Breathing mechanics, watch the volume and pressure graphs, switch Model to Bell jar, or turn Auto breathing off and drag the drawing. In Spirometer, wait for three quiet breaths, press Breathe in fully, then out fully (VC) and Forced expiration (FEV₁), then Record results. Change Lungs, Smoker and Activity and repeat. In Limewater practical, press Start breathing and compare the two tubes.

Parameters you can change

  • Screen Breathing mechanics, Spirometer, Gas exchange in the alveoli, Limewater practical
  • Model Chest, Bell jar
  • Lungs Healthy, Asthma (bronchoconstriction), Emphysema, Pulmonary fibrosis
  • Smoker
  • Activity Rest, Moderate exercise, Vigorous exercise

Questions to explore

  1. Why does air flow into the lungs when the diaphragm contracts and flattens?
  2. Why is the FEV₁/FVC ratio of a person with asthma lower than that of a healthy person?
  3. Which limewater tube turns milky first, and what does this show about exhaled air?

Related simulations